package com.dyz.leetcode._12_linkedList;

import com.dyz.leetcode.ListNode;

public class _148_sortList {
    public ListNode sortList(ListNode head) {
        if(head==null || head.next ==null){return head;}

        //找到中间值 快慢指针
        ListNode slow = head, fast = head.next;
        while (fast!=null && fast.next!=null){
            slow = slow.next;
            fast = fast.next.next;
        }

        ListNode righthead = slow.next;
        slow.next = null;


        ListNode left = sortList(head);
        ListNode right = sortList(righthead);


        ListNode listNode = mergeTwoLists(left, right);

        return listNode;

    }

    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        if(list1==null){
            return list2;
        }
        if(list2==null){
            return list1;
        }
        ListNode l1 = list1;
        ListNode l2 =list2;

        ListNode dummy = new ListNode(-1);
        ListNode curr = dummy;

        while (l1!=null &&l2!=null){
            if(l1.val<l2.val){
                curr.next = l1;
                l1 = l1.next;
            }else {
                curr.next = l2;
                l2 = l2.next;
            }
            curr = curr.next;
        }
        if(l1==null){curr.next = l2;}
        if(l2==null){curr.next = l1;}
        return dummy.next;
    }
}
